Piezoelectric sound-generating bodies are used in receivers, speakers and other parts of slim electronic devices and mobile electronic devices. These piezoelectric sound-generating bodies are constituted, for example, by storing, in a cap-shaped resin case, etc., a piezoelectric vibration plate formed by adhesively attaching on the principle side of a vibration plate made of phosphor bronze, etc., a piezoelectric element having surface electrodes formed on both principle sides of a disk-shaped ceramic piezoelectric substance. In recent years, high sound pressures and improved space efficiencies are required for the aforementioned devices as LCD displays and organic EL displays, etc., have become larger. To meet this demand, piezoelectric sound-generating bodies using bimorph piezoelectric elements are proposed as a means for achieving larger amplitudes.
One example of the aforementioned bimorph piezoelectric elements is presented by Patent Literature 1, which is a piezoelectric electro-acoustic converter having a bimorph piezoelectric element 111 as shown in FIG. 15. To be specific, a layered body is formed by stacking two or three piezoelectric ceramic layers 111d1, 111d2. Surface electrodes 111b1, 111b2 are formed on the two principle sides of this layered body, and an internal electrode 111a2 is formed between the ceramic layers 111d1, 111d2. Furthermore, all ceramic layers 111d1, 111d2 are polarized in the same direction, or specifically in the thickness direction, as indicated by the bold arrow. When alternating signals are applied between the surface electrodes 111b1, 111b2 and internal electrode 111a2 in the directions indicated by the thin arrows and in the opposite directions, for example, the layered body as a whole generates bending vibration.
On the other hand, Patent Literature 2 proposes a square piezoelectric electro-acoustic converter 120 having a piezoelectric element 121, as shown in FIGS. 16 and 17. This converter 120 has a pair of terminals 125a, 125b whose inner connection parts are exposed on the inner surface of the side wall of a case 124 in a direction roughly vertical to the piezoelectric element 121, and the inner connection parts of the terminals 125a, 125b are electrically connected to the surface electrodes (not illustrated) of the piezoelectric element 121 by lead conductors 128a, 128b made of conductive adhesive.
Patent Literature 1: Japanese Patent Laid-open No. 2001-95094
Patent Literature 2: Japanese Patent Laid-open No. 2004-15768